Most pet cats will become timid or defensive when outdoors, but not Millie – after being adopted by her mountain-climbing owner Craig Armstrong, Millie has become a feline hiking and mountain-climbing legend.

Rescued Dutch hikers exit a search and rescue snowcat after they were brought safely to Grotli, Norway, February 26, 2016. Thirteen Dutchmen who were stranded while hiking in central Norway's mountains were found after snowmobile patrols by the Red Cross. Snowcats from the Red Cross are now moving ahead to pick the hikers up. (Photo by Torstein Boe/Reuters/NTB Scanpix)

A journalist reports on a ladder outside the Great Hall of the People during the opening session of the National People's Congress (NPC) in Beijing, China March 5, 2018. The NPC has over 3,000 delegates and is the world's largest parliament or legislative assembly though its function is largely as a formal seal of approval for the policies fixed by the leaders of the Chinese Communist Party. The NPC runs alongside the annual plenary meetings of the Chinese People's Political Consultative Conference (CPPCC), together known as “Lianghui” or “Two Meetings”. (Photo by Thomas Peter/Reuters)

The sun rises between Sgurr nan Gillean and Knight’s Peak, Black Cuillin, Isle of Skye. (Photo by Adrian Trendall/Mountain Photo of the Year)

Jason Arnold, project manager from solarcentury walks between lines of solar panels erected at Weighbridge, Wheal Jane, Baldhu on July 7, 2011 near Truro, England. A ceremony was held today to mark the connection of the 1.4kw solar farm, which on a 6.2 acre plot is the first in the South West and biggest in the UK to date, using 5,680 panels. (Photo by Matt Cardy/Getty Images)

Britain Soccer Football, West Ham United vs Manchester United, Barclays Premier League, Old Trafford on May 10, 2016. Police play football with a young West Ham fan before the match. (Photo by Eddie Keogh/Reuters/Livepic)

People walk on a sightseeing platform in Zhangjiajie, Hunan Province, China, August 1, 2016. China has opened a 100-metre-long glass skywalk stretching around a cliff on the side of the Tianmen Mountain. The skywalk provides a view of a 300-metre drop and overlooks Tongtian Avenue, a mountain road with 99 turns that snakes up the mountain. When translated in English, it means “Avenue to the Sky”. (Photo by Reuters/Stringer)